As shown in FIG. 1, an architecture of a current worldwide interoperability for microwave access (WiMAX) mobile network includes a customer premises equipment (CPE) 101 of WiMAX, base stations (BS) 102 of an access network of WiMAX, access service network gateways (ASN-GW, access gateway for short herein) 103, a connection service network (CSN) 104 of WiMAX, and a packet data network (PDN) or synchronous digital hierarchy (SDH) 105, wherein the CPE 101, the BSs 102 and the ASN-GWs 103 form an access service network (ASN) of WiMAX. With respect to interconnection, a standard R1 interface is used between the CPE 101 and the BS 102, a standard R6 interface is used between the BS 102 and the ASN-GW 103, a standard R8 interface is used between BSs 102, a standard R4 interface is used between ASN-GWs 103, an R3 interface is used between the ASN-GW 103 and the CSN 104, and the PDN/SDH 105 is a transmission bearing network of WiMAX.
At present, the main frequency band of the radio frequency of a WiMAX system is 2.3/2.5/3.5 GHz, if a conventional outdoor-covering-indoor mode of integrated macro base stations is adopted, a high transmission loss is caused in a dense urban area, and generally, a transmission loss of 18-25 dB is budgeted, thus, the simple adoption of the outdoor-covering-indoor mode will certainly bring about the reduction in the outdoor coverage radius, the increase in outdoor stations and network construction costs and the difficulty in fast networking. In addition, conventional outdoor macro base stations and micro base stations cannot meet the requirements of enterprises and commercial buildings with high telephone traffic, which have high requirements on capacity, need a high signal-to-noise ratio in a coverage area, and are required to meet the demands on high-order modulation of 16QAM or even 64QAM.
Furthermore, the adoption of the conventional outdoor macro base station and micro base station cannot meet the requirements of enterprises and commercial buildings with high telephone traffic, which have a high requirement on capacity, need a high signal-to-noise ratio in a coverage area, and are required to meet the demands on a high-order modulation of 16QAM or even 64QAM.
In conclusion, for the network construction for WiMAX and future 4G, a Pico Cell mode is recommended to complement indoor coverage in an urban area and a dense urban area. The existing Pico Cell scheme includes a baseband unit+Pico RRU mode and an integrated Pico BS mode; the present invention focuses on improved schemes and device management based on integrated Pico BSs.
At present, common methods adopted by a mobile system for deploying access points are as follows:
Scheme 1: in a coverage area, multiple independently-configured access points Pico BSs are adopted and connected with the access gateway of a central equipment room via a transmission network, and this scheme is a demonstration for an indoor coverage network based on the conventional Pico BS architecture.
The network structure of this scheme is as shown in FIG. 2, in this structure, each coverage area (as shown in FIG. 2, an area on a floor) is deployed with Pico BSs 201, and multiple independent Pico BSs 201 are connected with each other via a converging switch or router 202, and the switch or router 202 provides an R6 interface connected to a transmission network PDN/SDH 203. Each Pico BS 201 should be configured with a GPS module to solve the synchronization problem of a TDD (time division duplex) system and prevent interference from system networking. Although access points in an area are physically neighboring to each other, no logical channel communication is provided among the access points, that is, no local access management unit is provided in the whole building or among building groups, in this case, communication among Pico BSs 201, including switching control information among base stations and user interface information interaction of users among the access points in the area, has to be firstly routed to the ASN-GW 204 of a central equipment room node via the PDN/SDH 203, then accessed to the CSN 205, processed and sent to a target base station, this wastes much bandwidth of an SDH/PDH network. On the other hand, the performance deterioration, such as the delay and jitter generated in the process of passing a router of a public network, degrades the user experience. In commercial buildings and central business districts (CBD) with large-intermediate capacity, switching services of the majority of users occur among floors, on floors and in elevators, and at hallway and other overlapped coverage location, and the switching may happen frequently. It is very difficult to realize indoor deployment in the conventional Pico BS architecture because a Pico BS in this architecture is required to support interfaces including twisted pair cables, optical fibers and coaxial cables, and to be configured with a GPS antenna for the sake of synchronization, further, the conventional Pico BS architecture is not beneficial for network capacity optimization and cannot realize many scenes or has to pay much for the realization.
Scheme 2: in a coverage area, a Pico/Micro/Pico BS is adopted to provide a signal source, and RF signals are distributed to multiple antenna units via a passive distributed system, and the power of each antenna unit is equal to that of an access point. This scheme demonstrates an indoor coverage network based on a signal source base station+passive distributed antenna system architecture, which is applicable to a small-scale indoor coverage network.
The network architecture of this scheme is as shown in FIG. 3, in this architecture, a signal source base station (BS) 301 may be a Micro BS or a Pico BS, specifically depending on the scale of indoor coverage and the network topology condition. The signal source base station provides RF (radio frequency) signals to a power divider 302 and a coupler 303, and through multi-level distribution, the signals are output to a ceiling antenna 304 or a wall-mounted antenna 305, the specific type of antennae is determined according to indoor terrain and network planning. The difference between the power divider 302 and the coupler 303 lies in that the former realizes equal power division and the latter realizes proportional distribution of power transmitted to different ports as required. In this scheme, a Pico/Micro/Pico BS provides a signal source, RF signals are distributed to multiple antenna units via a passive distributed system, and each antenna unit has a power equal to that of an access point. One of disadvantages of this scheme is that the signal source base station is required to provide a high power, because the passive distributed system has high transmission loss and is not applicable to large-scale or intermediate-scale indoor coverage system networking, and another one is that a large engineering construction-and-deployment workload is needed for the expansion of cell capacity.
Scheme 3: in a coverage area, a Pico/Micro/Pico BS (401) is adopted to provide a signal source, and RF signals are distributed to multiple antenna units via an active distributed system, with the power of each antenna unit being equal to that of an access point. This scheme is an indoor coverage network based on a signal source base station+active distributed antenna system architecture, which is applicable to a large-scale or intermediate-scale indoor coverage network.
The network architecture of this scheme is as shown in FIG. 4, in this architecture, the connections and the functions of a signal source base station 401, a power divider 402, a coupler 403, a ceiling antenna 404 and a wall-mounted antenna 405 are identical to those in an indoor coverage network based on a passive antenna system architecture shown in FIG. 3. The biggest difference between the active distributed system and the passive distributed system shown in FIG. 4 lies in that a trunk amplifier 404 is deployed at a middle trunk location having high signal attenuation to resist the loss caused by line transmission. As 802.16e refers to a TDD system having strict requirements on time synchronization, the trunk amplifier 404 can extract transmit/receive time-sequence synchronization signals and compensate the symbol transmit/receive time sequence brought by the delays of different lines. In this scheme, a Pico/Micro/Pico BS is adopted to provide a signal source, RF signals are distributed to multiple antenna units via an active distributed system, the power of each antenna unit is equal to that of an access point, and a trunk amplifier 404 is added to a transmission line to compensate line losses. This scheme is applicable to a large-scale or intermediate-scale indoor coverage network but is not beneficial for post capacity expansion; in addition, the TDD system is required to solve the problems of coexistence with the existing system and the accompanying increase in the cost of intermediate nodes, as well as large costs and workloads of maintenance and capacity expansion, and also lower system reliability, etc.
Although the above is exampled by a WiMAX system, wireless access systems and methods in other existing indoor coverage scenes or mixed indoor and outdoor coverage scenes also have the following disadvantages:
1) the requirement on indoor cable resources is high, e.g., ample optical fibers, twisted pair cables or coaxial cables and other distributed systems are needed; partial operators (particularly, transnational operators in emerging markets) provide neither optical fiber resources nor twisted pair cable resources in the most majority of buildings, so it is very difficult to rate up network construction and reduce deployment cost;
2) in order to share existing distributed systems, considering the particularity of a TDD system, part of existing operators, who have realized 2G/3G indoor coverage, are required to make much modification to indoor antennas and filters, and the workload thereof is tremendous, moreover, the modification will interrupt existing network services, and cannot realize a smooth network upgrade;
3) as for the construction of a new piece of independent indoor distribution engineering, it is difficult to proceed the deployment, and it is necessary to modify the existing spatial structure, bringing about a difficulty in engineering coordination;
4) in a large-scale or intermediate-scale indoor coverage scene, the configuration of a Pico BS with GPS requires tremendous installation workloads and extreme high maintenance costs if multiple Pico BSs are required to be deployed;
5) an independent Pico BS has problems in management, local maintenance, and degradation in switching performance;
6) information interaction between independent Pico BSs lowers transmission efficiency;
7) an independent Pico BS brings about problems in performance statistics, performance bottlenecks and expansion of a centralized network management unit in version upgrade;
8) indoor distributed systems have problems in capacity expansion, scale and performance.